Microphone.



PATENTED JUNE 4, 1907.

N. H.-H0LLAND.

MICROPHONE.

APPLICATION FILED JULY 28. 1906.

- ticularly for assisting the hearing of deaf persons; to

small movement of the causing the transmission of soundifrom exphone provided UNI ED sTATEs PATENT OFFICE.

N H. HOLLAND, OF-

CHICAGO, ILLINOIS, ASSIGNOR, BY DIRECT AND MEsN ASSIGNMENTS, To ERNEST H. s oLz,

OF CHICAGO, ILLINOIS.

MICROPHONE.

Specification of Letters Patent.

Patented June 4, ,1907.'

Application filed July 28,1906. Serial No- 328,175.

To all whom, it may concern:

Be it known that I, NEWMAN H. HoLLANn, a subject of the King of Great Britain and Ireland, and a' resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Microphones, of which the following is a specification. The main objects of this invention are to provide a microphone which is extremely sensitive to weak sounds and which is parapplicable for use in instruments provide a form of microphone which is adapted to operate in conjunction with the diaphragm of a telephone transmitter and which, while offering a minimum resistance to the vibration of the diaphragm, will cause a large variation in the resistance to the electric current between the. electrodes for a diaphragm, thereby t'remely delicate vibrations of the diaphragm; and to provide electrodes of suitable form to retain a quantity of carbon granules without requiring a retaining envelop of material such as cloth, as is usually done. I accomplish these objects by the deviceshown in the accompanying drawings, in which: 30

igurel is a view showing the general arrangement of the parts of a pocket auro- ,with a microphone transmitter constructed according to this invention. Fig. 2 is a-sectionof the transmitter 011' the line 2,-2 of Fig. 1. Fig. 3 is a rear view of the same with the cover removed. Fig. 4 is a detail partly broken away showing the arrangement of the stop which limits the separation of the electrodes.

In the construction shown in the drawings, the transmitter 5 is mountedin a fixed'position at one end of a pocket battery 6 and the receiver 7 is electrically connected'with the transmitter and batteryby the conductors 8. The receiver is preferably provided with a switch rodhaving a button 9 at each end for throwing the batteries in and ,out of circuit with the receiver and transmitter.

The transmitter. 5 consists of a hollow cylindrical casing provided in its front face with, apertures 10 for the passage of i sound Waves into the interior.

a plurality of Adiaphragm '11- preferably of carbon and forming one of the electrodes of the microphone, extends across the-interior the apertures 10.

A lever 12 is carried by a spindle 13 which of the casing 5 inward of is delicately pivoted between the adjusting j phragm and forming a retainer or pocket which supportsbetween it and said draphragm a quantity of granules of material The other end of the lever 12 is weighted which is a conductorof electricity, preferably carbon. These granules- 17 are preferably spherical in form and of uniiorm'size. movement of the electrode 16 away from the diaphragm 11 is limited by means of an adjustable stop which prevents the separation The of the electrodes sufficiently to permit the granules 17 to fall out.v The adjacent faces of the electrode'16 and diaphragm 11 converge at, theedges of the electrode. .When

the transmitter is held upright the weightof.

-the granules 17 causes the same to'wedge between the diaphragm and the inclined walls of the electrode trode'away'from the diaphragm. A light torsion spring 19 urges the electrode 16 toward the diaphragm 11 with the desired initial pressure. The pressure of this spring overcomes the tendency of the carbon granules to separate the electrodes and brings'the electrodes to a position'where they'are nearly but not quite in contact with each other. 1

The operation of the device is as follows: The user holds the receiver" 7 to his can and throws'on the current by pressing the button 9. The battery and transmitter are carried in his pocket, with the front of the transmitter -facing away from his body so as to be readily reached by sound waves. When-the diaphragm is I at rest, th

16 and urge said elec e pressure upon'the carbon particles between the electrodes. is

extremely light owing to the perfect balance of the lever, andthe tendency of thespring ."to counteract the effect of the weight of the granules in separating the electrodesq The spherical-form of the carbon granules perceases the intervening carbon granules varies a considerable range for comparatively movements of the diaphragm. This rise to variations in the electric current ch are changed into sound. waves by the 'ver in the usual way. 1 Wi lie-t I claim as my invention. and desire to secure by Letters Fatent is:

' A microphone comprising an electrode aged to be vibrated by sound waves, a road electrode pivotally mounted at its r ofgravity and having apart adjacent first electrode, a spring normally urgthc pivoted electrode toward-the other,

,granules of conducting material interrally urge said electrodes apart.

iicrophone comprising an electrode ed-to be vibrated by sound waves, a ed electrode pivotally mounted at its ,r-o'f gravity and'having a part adjacent e'iirst electrode, aspring normally ur the pivoted-electrode toward the other, ice of conducting material interposed on said electrodes and arranged'to norge saidelectrodes apart, and a step e to limit thepivotal movement of i lever.

v A microphone comprising a diaphragm at-rode arranged to-vibrate for transmiti l anarm pivotally mountedand llilg thereon an electrode adjacent to the neans normally urging said electrodes i each other, granules ol, conducting aerialinterposed/between said "electrodes adapted through. gravity to urge them :1 art and a stop forlimiting the pivotal 7 x increment of said arm.

*etween said electrodes and arranged i the diaphragm so that the pressure- 4. A microphone comprising a diaphragm electrode; a second electrode adjacent to the first, pivotally mounted at its center of gravity and having a relatively high inertia; a spring normally urging the pivoted electrode toward the ther, the adjacent iaces of said electrodes being inclined toward each other; granules of conducting material interposed )etween said electrodes and adapted through gravity to normally ur c said electrodes apart; and. a stop adapts to limit the separation. or" said electrodes. v

5. A microphone comprising an electrode arranged to transmit sound, a second else-= trode havii'ig a cupped face adjacent to the first and. forming a retainer for granular particles, a plurality of granules oi conducting material substantially uniform in size seated in said retainer, the cupped face of said electrode having walls inclined toward the first electrode whereby said granules will nor mally tend through their weight to urge said electrodes apart, a spring normally urging said electrodestoward each other, and a stop adapted to limit the separation of said electrodes to a distance less than thediameter' of said. granules.

6. A microphone comprising a vertically disposed diaphragm electrode arranged to Vibrate for transmitting sound, an electrode pivotally mounted on a horizontal axis substantially parallel with said diaphragm, said pivoted electrode being normally urged toward the diaphragm and having a surface below, its axis and conver ing downwardly toward the diaphragm, an ranules of con ducting material interposet between said. surface and the diaphragm and. tending to urgesaid electrodes apart.

Signed at Chicago this 26th day of J uly 1906.

NEVIMAN H. HOLLAND.

Witnesses:

E. A. RUMMLER, L. A. SMITH. 

